The present invention relates to a conversion die for completing can ends such as used on beverage containers and the like, and more particularly to a conversion die having a control apparatus for detecting double can ends and for terminating operation of the conversion die in response to the detection of a double can end.
A conventional conversion die for can ends consists of a number of die-punch machine assemblies positioned at work stations along a machine work path which can ends are caused to follow. The various die-punch machine assemblies perform different operations on a can end as it travels along the work path. For example, one machine assembly may make a groove to provide a weakened zone to form a pop-top opening; another machine assembly may place an identifying mark on the can end. Upon entering the conversion die, a can end has an initially stamped configuration with a generally flat circular body portion; an axially extending rim portion, integrally formed with the circular body portion; a radially extending flange portion, integrally formed and extending radially outwardly from the rim portion; and an arcuate generally axially extending lip portion integrally formed with the flange portion. In operations performed at the various work stations within the conversion die the can end is given the configuration which it will have just prior to being mounted on a can.
The can ends are operated on one at the time at each work station and pass through the machine horizontally in a side-by-side progression. However, the can ends are fed into the conversion die from a feeder in which they are positioned in a vertical stack. Sometimes two can ends which are stacked one on top of the other stick together and enter the conversion die as a "double can end". In most cases a "double can end" is created during an earlier rolling process which forms the arcuate lip portion of the can ends. Lips of two separate ends are occasionally rolled together, thus "locking" the ends together in a coaxial stacked relationship. At other times, a double can end is caused simply by surface adherence of two separate can ends.
When a double can end enters the machine the relatively greater thickness of the double can end may cause damage to some of the operating assemblies within the conversion die. It is thus desirable to detect the presence of a double can end immediately upon entrance thereof into the conversion die, so that operation of the conversion die may be terminated.